// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2023 Red Hat
 */

#include "index-page-map.h"

#include "errors.h"
#include "logger.h"
#include "memory-alloc.h"
#include "numeric.h"
#include "permassert.h"
#include "string-utils.h"
#include "thread-utils.h"

#include "hash-utils.h"
#include "indexer.h"

/*
 * The index page map is conceptually a two-dimensional array indexed by chapter number and index
 * page number within the chapter. Each entry contains the number of the last delta list on that
 * index page. In order to save memory, the information for the last page in each chapter is not
 * recorded, as it is known from the geometry.
 */

static const u8 PAGE_MAP_MAGIC[] = "ALBIPM02";

#define PAGE_MAP_MAGIC_LENGTH (sizeof(PAGE_MAP_MAGIC) - 1)

static inline u32 get_entry_count(const struct index_geometry *geometry)
{
        return geometry->chapters_per_volume * (geometry->index_pages_per_chapter - 1);
}

int uds_make_index_page_map(const struct index_geometry *geometry,
                            struct index_page_map **map_ptr)
{
        int result;
        struct index_page_map *map;

        result = vdo_allocate(1, "page map", &map);
        if (result != VDO_SUCCESS)
                return result;

        map->geometry = geometry;
        map->entries_per_chapter = geometry->index_pages_per_chapter - 1;
        result = vdo_allocate(get_entry_count(geometry), "Index Page Map Entries",
                              &map->entries);
        if (result != VDO_SUCCESS) {
                uds_free_index_page_map(map);
                return result;
        }

        *map_ptr = map;
        return UDS_SUCCESS;
}

void uds_free_index_page_map(struct index_page_map *map)
{
        if (map != NULL) {
                vdo_free(map->entries);
                vdo_free(map);
        }
}

void uds_update_index_page_map(struct index_page_map *map, u64 virtual_chapter_number,
                               u32 chapter_number, u32 index_page_number,
                               u32 delta_list_number)
{
        size_t slot;

        map->last_update = virtual_chapter_number;
        if (index_page_number == map->entries_per_chapter)
                return;

        slot = (chapter_number * map->entries_per_chapter) + index_page_number;
        map->entries[slot] = delta_list_number;
}

u32 uds_find_index_page_number(const struct index_page_map *map,
                               const struct uds_record_name *name, u32 chapter_number)
{
        u32 delta_list_number = uds_hash_to_chapter_delta_list(name, map->geometry);
        u32 slot = chapter_number * map->entries_per_chapter;
        u32 page;

        for (page = 0; page < map->entries_per_chapter; page++) {
                if (delta_list_number <= map->entries[slot + page])
                        break;
        }

        return page;
}

void uds_get_list_number_bounds(const struct index_page_map *map, u32 chapter_number,
                                u32 index_page_number, u32 *lowest_list,
                                u32 *highest_list)
{
        u32 slot = chapter_number * map->entries_per_chapter;

        *lowest_list = ((index_page_number == 0) ?
                        0 : map->entries[slot + index_page_number - 1] + 1);
        *highest_list = ((index_page_number < map->entries_per_chapter) ?
                         map->entries[slot + index_page_number] :
                         map->geometry->delta_lists_per_chapter - 1);
}

u64 uds_compute_index_page_map_save_size(const struct index_geometry *geometry)
{
        return PAGE_MAP_MAGIC_LENGTH + sizeof(u64) + sizeof(u16) * get_entry_count(geometry);
}

int uds_write_index_page_map(struct index_page_map *map, struct buffered_writer *writer)
{
        int result;
        u8 *buffer;
        size_t offset = 0;
        u64 saved_size = uds_compute_index_page_map_save_size(map->geometry);
        u32 i;

        result = vdo_allocate(saved_size, "page map data", &buffer);
        if (result != VDO_SUCCESS)
                return result;

        memcpy(buffer, PAGE_MAP_MAGIC, PAGE_MAP_MAGIC_LENGTH);
        offset += PAGE_MAP_MAGIC_LENGTH;
        encode_u64_le(buffer, &offset, map->last_update);
        for (i = 0; i < get_entry_count(map->geometry); i++)
                encode_u16_le(buffer, &offset, map->entries[i]);

        result = uds_write_to_buffered_writer(writer, buffer, offset);
        vdo_free(buffer);
        if (result != UDS_SUCCESS)
                return result;

        return uds_flush_buffered_writer(writer);
}

int uds_read_index_page_map(struct index_page_map *map, struct buffered_reader *reader)
{
        int result;
        u8 magic[PAGE_MAP_MAGIC_LENGTH];
        u8 *buffer;
        size_t offset = 0;
        u64 saved_size = uds_compute_index_page_map_save_size(map->geometry);
        u32 i;

        result = vdo_allocate(saved_size, "page map data", &buffer);
        if (result != VDO_SUCCESS)
                return result;

        result = uds_read_from_buffered_reader(reader, buffer, saved_size);
        if (result != UDS_SUCCESS) {
                vdo_free(buffer);
                return result;
        }

        memcpy(&magic, buffer, PAGE_MAP_MAGIC_LENGTH);
        offset += PAGE_MAP_MAGIC_LENGTH;
        if (memcmp(magic, PAGE_MAP_MAGIC, PAGE_MAP_MAGIC_LENGTH) != 0) {
                vdo_free(buffer);
                return UDS_CORRUPT_DATA;
        }

        decode_u64_le(buffer, &offset, &map->last_update);
        for (i = 0; i < get_entry_count(map->geometry); i++)
                decode_u16_le(buffer, &offset, &map->entries[i]);

        vdo_free(buffer);
        vdo_log_debug("read index page map, last update %llu",
                      (unsigned long long) map->last_update);
        return UDS_SUCCESS;
}